Disc sector and method of assembly thereof



. United States Patent 1 1 3,539,050 7 72 Inventors Steven s. Davis [50] Field oiSearch 210/486 1 Bountiful, and

Kent L. Davis and John C. Brozovich, Salt [56] References Cited Lake City, Utah UNITED STATES PATENTS 211 App]- No. 653. 2,8l3,632 11/1957 Muller 2l0/486 [22] ,F1led July 17,1967 3,019,905 2/1962 Baker et 8| 210/486 [45] Patented NOV. 10, 1970 i 3,291,3l2 l2/l 966 Peterson 2 l 0/486X [73] As.slgnee Emil-ouch corpora Primary Examiner-John W. Adee 1 Sill Lake City, Utah A C H G Id d R be R F. h

a corponfion of Delaware ttorneyarvey 0 an 0 rt Inc [54] DISC SECTOR AND METHOD OF ASSEMBLY THEREOF 3 Claims, 4 Drawing Figs.

52 tJ.s.c| 210/486 511 1111.0. ..B0ld33/26 the sector is conformed by localized softening and cooling of I the sector while in place against the adaptor wall.

Patented no. 10, 1970- V 7 3,539,050

Sheet 3 of-2 42 U? I i I ,4

. -40 36 FIG. 4

' I\IV1NTORS. 7 F28 STEVEN s. DAVIS KENT L. DA IS JOHN c. BRO BY: A/ J l I FIG. 3 C

This invention relates generally to filter disc sectors of the fitted over itsapex for securing it to a rotating center shaft on a filter. More particularly, it relates to a method for securing a thermoplastic sector to a metal adaptor to form a sector assembly, and to a sector assembly formed in accordance with the invention. I

The'primary object of the invention is to provide a disc sector assembly comprising a sector of thermoplastic material and a metal bell adaptor rigidly secured together as an integral unit.

Another important object is to provide a novel and inexpensive method for locking a metal bell adaptor and a thermoplastic sector together to form a rigid assembly and for easily separating said adaptor and sector.

Briefly the apparatus invention'compris'es a disc sector assembly having a thermoplasticresin sector fitted to a metal bell adaptor and locked thereto by virtue of the plastic material irregularities in the adaptor walls.

The method invention comprises the steps of pressing the thermoplastic sector into a bell adaptor and maintaining the temperature of the adaptor high enough to soften the plastic until it conforms to irregularities in the wall surface of the adaptor then cooling the assembly to solidify the plastic whereby it cooperates with the wall irregularities to form a lock.

So that the invention may be more readily understood and carried into effect, reference is made to the accompanying drawings which are offered by way of example only and are not to be taken as limiting the invention, the scope of which is defined by the appended claims which obviously embrace equivalent structures.

In the drawings:

FIG. 1 is a perspective view of a conventional rotary disc filter showing a filter disc formed from eight disc sectors attached to hell adaptors whichare mounted on a rotatable shaft. For convenience, only one disc is shown in the'drawings.

FIG. 2 is a plan view of a discsector secured to a bell adapfilter medium.

tureIthan the sector-material. If a strong high melting plastic is i i available it maybe substituted for the metal bell and the adap- I tor may be of different sha e or design. type comprising aw'edge shaped sectorhaving a bell adaptor 1 I tor. The disc sector is shown partially coveredwith a suitable FIG. 3 is an enlarged plan view of a belladaptor shown partially broken away to illustrate an irregularity in the form of a cavity in the adaptor's sidewall for locking it to the sector.

FIG. 4 is a sectional view taken in the plane of line 4-4 of FIG. 2.

FIG. 1 illustrates a rotary disc filter comprising an elongated slurry tank 10 with at least one filter disc 12 secured to a rotatable tubular shaft 14 journaled in bearings 16 at the tank ends. Scrapers 18 are provided adjacent the disc facesto assist in cake discharge and direct cake into a collection bin 20. Slurry to be filtered is supplied through a suitable inlet 22. Filtrate is drawn through a filter medium 30 covering each sector thence through a port into the tubular shaft for eventual discharge.

A complete disc is formed from several sector assemblies and each sector assembly comprises a sector 26 rigidly secured to a bell adaptor 28 by which the assembly'is in turn mounted on the center shaft. As is usual, the sector comprises a wedge shaped base 32 having surface ridges 34 for supporting filter cloth and directing flow to the bell adaptor.

The sector is cast, molded or otherwise formed from thermoplastic material, such as polyethylene, polypropylene. cellulose propionate, acrylate, polyvinyl chloride, and the like, having a softening temperature below that of the bell.

The bell adaptor 28 may be of conventional design having interior sidewalls 36 tapering inwardly from its receiving end 38 to a discharge stub 40 which connects it to the tubular shaft 14. The adaptor is usually constructed from a strong metal, such as cast iron-or steel, having a higher softening tempera- For assembly, the adap or and sector are pressed together the irregularity, is maintained above the softening temperature of the sector and the sector pressed in place. Softening temperature of a material is defined as the temperature at which the material readily deforms and flows when a pressure is applied to it. The bell may be heated before or after the sector is fitted to it, but in either case the elevated temperature is maintained sufficiently long so that the sector material softens and conforms to the adaptor walls then is permitted to cool to solidify the plastic.

To provide the positive lock between the adaptor and sector an irregularity,such as a port 42, is provided in at least one sidewall of the adaptor. Upon assembly, the sector is pressed 'into the adaptor andthe temperature of the sector, at least in the area of the port 42, is maintained above thesoftening temperature of the sector until sector material flows into or around the irregularity, then the assembly is cooled so'the plastic material solidifies in the port and a positive mechanical lock is formed.

Although in the illustrated embodiment, plastic has solidified in the port to act as a lock, obviously the irregularity may take other forms such as corrugations, pins or lugs and the like about which the plastic may form.

To separate the sector and bell it is only necessary to reheat and pull them apart. it is not necessary that the entire adaptor be heated and a suitable lock will be obtained if only that part of the bell containing the irregularity is heated.

The following examples will illustrate the mode of practice of this invention and will demonstrate the results obtainable therefrom:

EXAMPLE I A cast iron bell adaptor having tapered interior sidewalls and provided with small ports in the walls was heated to a temperature of about 400F. The apex of a wedge-shaped p'olyproplene resin disc sector, having a softening temperature of about 340F., was then pressed into the receiving end of the EXAMPLE 2 The wall of an iron adaptor with a port provided in one of sidewalls, was heated to a temperature of about 250F. at the areas near the port. The apex of a wedge-shaped polyethylene resin disc sector,'having a softening temperature of about 200F., was then pushed into the receiving end of the adaptor so that plastic was softened to flow through the port. The adaptor was then cooled to solidify the plastic so the material 'in the port formed a solid pin locking the two pieces together.

We claim:

1. A rotary filter disc sector assembly comprising a wedgeshaped sector formed from thermoplastic material, a metal bell adapter for mounting on a rotatable shaft fitted to the apex end of said sector, an irregularity in the wall of said adapter, and the thermoplastic material of said sector being conformed to said irregularity.

2. A sector assembly in accordance with claim 1 in which said irregularity comprises an opening in the adaptor wall. 

